This invention relates to a method and apparatus for forming a coreless armature winding for an electric machine and, more particularly, to such a method which can be readily implemented by automatic machinery, and to that machinery.
A coreless armature winding is a winding of wire that is not supported on or wound about a core. By eliminating the core, the overall mass and weight of the machine, such as a motor, advantageously is reduced. Because of this, motor operation is improved, and the control circuitry thereof can be simplified.
One type of technique for forming such a coreless armature winding uses a mandrel whose surface is honeycombed for forming and shaping the armature winding accordingly. The wire is wound about the honeycombed surface of the mandrel so as to form a cylindrical, honeycombed winding. Then, this winding is removed from the mandrel and the cylinder is flattened. This results in a winding that is substantially belt-shaped, yet retains the honeycomb configuration. Opposite ends of this belt shape are joined end-to-end so is to form the cylindrical armature winding of honeycomb shape. Unfortunately, forming such a coreless armature winding in accordance with the aforementioned manner requires a large number of intricate steps. Hence, this technique is time consuming and, thus, expensive. Furthermore, only low volumes of production can be attained by using this method. Also, a relatively large number of manual steps are needed, such as the removal of the honeycombed winding from the mandrel, thus making it difficult to automate this technique. Consequently, this method is not suitable for the large-scale manufacture of coreless armature windings.
In accordance with another technique for forming a coreless armature winding, a cylindrical winding surface is provided with a number of radially projecting guide pins. These pins are arranged in accordance with the winding configuration and also with the number of poles that the winding is to have. Then, the wire which is used to form the winding is wound about the guide pins. Each pin may be associated with a plurality of different turns so that the wire which is wound about the cylindrical winding surface exhibits many cross-overs. This technique results in a cylindrical armature winding of the so-called skew winding type. Although this method provides a winding which appears as a neat arrangement on the winding surface of the cylinder, the fact that several turns of wire overlap at each guide pin presents the danger that the insulation which coats the wire may rub away or peel off. This means that there is a high likelihood of a short-circuit between adjacent layers of the winding. Furthermore, since a number of turns is wound about each guide pin, the size, or thickness, of the wire, and particularly the outer diameter thereof, must be limited. This can result either in an undesirably thin coating of insulation or an undesirably thin gauge of wire.